Enhanced heat transfer surface and apparatus and method of manufacture

Claim 1

A heat exchanger tube for use in transferring heat between a boiling fluid in contact with the exterior surface of the tube and a fluid flowing through the interior of the tube comprising: at least one radially extending helical fin convolution formed on the exterior surface along the longitudinal axis of the tube having a distal single tip portion and a proximate root portion, the radial height of all of said radially extending helical fin convolutions along the longitudinal axis are generally the same, said single tip portion inclined toward the next adjacent convolution of said radially extending helical fin convolution which is inclined in the same direction as said single tip portion, said inclined single tip portion defining a subsurface channel between adjacent convolutions of helical fins, said subsurface channel having alternating closed portions where said inclined single tip portion contacts an adjacent helical fin convolution and open pores where said inclined tip portion is spaced from an adjacent helical fin convolution, and the boiling fluid in contact with the exterior surface of the tube communicates with said subsurface channels, and a worked interior surface of the tube wherein said worked interior surface has between thirty-six and forty-eight ribs about the interior circumference of the tube.